Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, UK.
Sci Rep. 2018 May 9;8(1):7343. doi: 10.1038/s41598-018-25793-y.
Across the animal kingdom, examples abound of individuals coming together to repel external threats. When such collective actions are initiated by recruitment signals, individuals may benefit from being selective in whom they join, so the identity of the initiator may determine the magnitude of the group response. However, the role of signaller discrimination in coordinating group-level responses has yet to be tested. Here we show that in wild jackdaws, a colonial corvid species, collective responses to anti-predator recruitment calls are mediated by caller characteristics. In playbacks next to nestboxes, the calls of nestbox residents attracted most recruits, followed in turn by other colony members, non-colony members and rooks (a sympatric corvid). Playbacks in fields outside nestbox colonies, where the immediate threat to broods was lower, showed similar results, with highest recruitment to nearby colony members' calls. Responses were further influenced by caller sex: calls from non-colony member females were less likely to elicit responsive scolding by recruits than other calls, potentially reflecting social rank associated with sex and colony membership. These results show that vocal discrimination mediates jackdaws' collective responses and highlight the need for further research into the cognitive basis of collective actions in animal groups.
在动物王国中，有许多个体聚集在一起抵御外部威胁的例子。当这种集体行动是由招募信号引发时，个体可能会从选择性地加入谁中受益，因此发起者的身份可能决定群体反应的规模。然而，信号者歧视在协调群体水平反应中的作用尚未得到检验。在这里，我们表明，在野生松鸦中，一种群居的鸦科鸟类，对捕食者招募叫声的集体反应是由叫声特征介导的。在巢箱旁边的回放中，巢箱居民的叫声吸引了最多的招募者，其次是其他群体成员、非群体成员和红隼（一种同域鸦科鸟类）。在巢箱群体外的田野中进行的回放中，由于对雏鸟的直接威胁较低，结果相似，对附近群体成员叫声的招募最多。反应还受到叫声者性别的影响：非群体成员雌性的叫声比其他叫声更不可能引起被招募者的回应性责骂，这可能反映了与性别和群体成员身份相关的社会等级。这些结果表明，声音辨别介导了松鸦的集体反应，并强调了需要进一步研究动物群体中集体行动的认知基础。
